How can a Muslim girl be guided by name only, who was raised Christian, and wishes to embrace Islam and completely abandon Christianity?

The matter of Islam is grave; it is the path to eternal bliss for whoever follows it. Allah has abrogated all other religions with Islam, and after the advent of Prophet Muhammad (peace be upon him), Allah accepts no religion other than it.

Allah the Almighty says: "And whoever desires a religion other than Islam, it will never be accepted from him, and in the Hereafter he will be among the losers." (Quran 3:85). Seeking knowledge is an obligation upon every Muslim, and whoever fails to seek it commits a sin.

Allah the Almighty says: "So ask the people of the message if you do not know." (Quran 21:7). It is incumbent upon a Muslim to perform the obligatory duties, such as prayer, and abandoning it is one of the major sins.

Allah the Almighty says: "So woe to those who pray, [But] who are heedless of their prayer." (Quran 107:4-5). A Muslim's going to a church and witnessing forbidden acts may lead to disbelief (kufr).